Japanese Patent Application Laid-open No. 2005-58733 (Document 1) and Japanese Patent Application Laid-open No. 2007-89650 (Document 2) propose an exercise assisting device that tightens and relaxes muscle groups of the thighs without hardly any bending or stretching of the knees by displacing a seat member provided therein with the feet of a user placed on a foot rest and the buttocks of the user supported by a bearing surface of the seat member. This exercise assisting device varies the user's own weight that acts on the legs by displacing the position of the seat member to vary the proportion of the user's body weight that supports the seat member.
According to this operation, together with reducing the load on the user's legs as compared to that in the case of allowing the user's entire body weight to act thereon, muscles of the thighs can be contracted without hardly any bending or stretching of the knees, thereby making it possible to strengthen muscle groups of the thighs even for users having knee pain in the manner of diabetes patients, for example. Moreover, since muscle groups of the thighs have large volume, use of this device is expected to contribute to improvement of lifestyle diseases due to metabolism of sugar accompanying muscle contraction. What is more, since the user can exercise passively without having to spontaneously exert muscle force by allowing the seat member to be displaced by a driving source, coupled with the light load, even users whose motor functions have been diminished are able to use the device.
However, since the exercise assisting device having the configuration described above allows muscle groups of the thighs to be tightened and relaxed by varying the user's own weight that acts on the legs with the knee joints bent at a predetermined angle unaccompanied by hardly any bending or stretching of the knees in the manner of so-called squat exercises that do not involve bending or stretching, this device offers the advantage of enabling even users having knee pain to strengthen muscle groups of the thighs.
On the other hand, in the case of ordinary users who do not have knee pain, an exercise device is sought that provides exercise effects even if there is some degree of bending and stretching of the knee joints during exercise, and low price and compact size are frequently used as conditions for selecting such a device. However, according to the technology described in Document 1 and Document 2 above, in order to allow exercising without varying the bending angle of the knees, the device has problems that result in the use of a large number of components and large size, such as restrictions on the direction of movement of the seat member and the need for a mechanism to vary the positions of the feet accompanying swinging of the seat member.